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  • 1.
    Deng, Liang
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Investigation and simulation of tool wear in press hardening2014Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Due to the requirements of higher strength components and lower carbon dioxide emission, press hardening becomes prevalent in the automotive industry. Heating a boron alloyed steel blank to obtain the austensite phase at high temperature and quenching it to martensitic phase enhances the strength of the products and still allows complex shapes. However, the stamping tool has to endure severe temperature changes, impacts of the counterpart and sliding processes. The wear including material transfer, surface scuffing and complicated reactions between coatings and superficial oxide layers not only shortens the service-life of tools but also decreases the productivity and the quality of the manufacturing process. Furthermore, the harsh contact conditions between the stamping tools and the work-piece, regarded as the reason for the wear, are difficult to measure in situ. The fundamental study on the tool wear in the press hardening receives insufficient attention. The present work aims at establishing an understanding of tribological characteristics in press hardening and at developing a predictive wear model by establishing a relationship between the contact conditions and the wear process. Based on these results, the extension of the service life of stamping tools through adjustment of process parameters can be possible. Sliding wear, as the dominant wear phenomenon taking place during press hardening processes, causes formation of wear particles and transfer of material fragments to the tool surface. Since the wear process is dependent on the contact conditions, finite element (FE) simulations based on thermo-mechanical calculations are used to investigate the contact conditions in a given press hardening process. Based on the results from the FE--simulations, reciprocating tests and tribolgical tests are conducted respectively under press hardening conditions to evaluate the wear coefficients of the Archard's wear model. A modified wear model is implemented in the FE--simulations to predict wear depths on the stamping tools. It is noted that most wear concentrates on the tool radius and that it correlates with the sliding distance. The correlation between the experimental set-ups and the wear predictions are analysed. An industrial experimental set-up for validation of the wear model predictions has been developed. The future work on this study is outlined.

  • 2.
    Deng, Liang
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Modelling of wear and galling in press hardening simulations2017Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Implementation of press hardened parts in automobile responses to the requirement of reduced carbon dioxide emission because the press hardened part has very high ratio of strength to weight. Furthermore, ultra high-strength steels (press hardened parts) increases the vehicle safety. The press hardening processes are prevalently applied in global automotive industries. However, the press hardening processes corresponding to heating, forming, and cooling processes result in harsh contact conditions such as cyclic pressures, high temperatures and complex reactions between coatings and tool steels. Consequently, these harsh contact conditions increase the tool maintenance due to abrasive wear and adhesive wear. In order to study tribological behaviours in the press hardening, two kinds of the tribological experiments have been developed and used. Firstly, a reciprocating test, also called SRV test, is performed at elevated temperatures to study the wear mechanisms under press hardening conditions. However, the discrepancy between the press hardening and SRV test is obvious. To overcome the disadvantage, a sliding tribometer, also called tribolgoical test, is used as the second tribological test. A unidirectional sliding process is running under the corresponding pressures, temperatures, velocities and sliding distances. These test parameters are based on press hardening simulations. According to the present study, the abrasive wear is the predominant wear mechanism in the uncoated interface of the press hardening processes. When Al-Si coated workpieces are applied in the press hardening, severe adhesive wear, also called galling, substantially occurs in the stamping tool. The modelling of the abrasive and adhesive wear is derived from the Archard wear model in which the specific coefficients for the wear are calibrated by the tribological tests. The wear predictions implemented in the press hardening simulation have been validated by a press hardening experiment, which represents a typical geometry of vehicle components.

  • 3.
    Deng, Liang
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Mozgovoy, Sergej
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Development of a Tribological Test Programme Based on Press Hardening Simulations2017Ingår i: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 65, nr 2, artikel-id 43Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Press hardening is widely utilized to form ultra-high-strength steels characterized by a high strength-to-weight ratio for automotive components. Press hardening processes include heating boron–manganese steels to austenite phase, forming the steels at a high temperature, and cooling the formed blanks until the martensite phase is reached . However, press hardening processes lead to severe contact conditions between the blank and the tools including contact pressure, relative sliding, and high temperatures, which result in tool wear and increased maintenance cost. The contact conditions that occur in the stamping tool are difficult to study on site. Additionally, simplified tests, such as pin on disc and ball on disc, are insufficient to reproduce press hardening conditions in laboratory environments . The aim of this study includes developing a tribological test with press hardening conditions in which tool steel pins continuously slide on fresh and hot boron–manganese steel strips. The test programme mimics press hardening conditions with respect to sliding distance, sliding velocity, contact pressure, and surface temperature that were studied based on finite element (FE) simulations of a press hardening experiment. Furthermore, a FE simulation of the tribological test is established and it provides contact temperature in the pin tip with a high accuracy. A tribological test is used to study friction and mass loss with variational pressures and velocities that represented typically variational contact conditions in the press hardening. The tribological test is also used to obtain correlations between the tribological behaviours and process parameters in press hardening including pressure and sliding velocity.

  • 4.
    Deng, Liang
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Mozgovoy, Sergej
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Implementation of wear models for stamping tools under press hardening conditions based on laboratory tests2014Ingår i: Advanced Materials Research, ISSN 1022-6680, E-ISSN 1662-8985, Vol. 1063, s. 339-342Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Tool wear occurring in press hardening processes receives insufficient attention since its corresponding measurements and full-scale experiments are complicated and expensive. This paper presents a study of tool wear in press hardening based on laboratory experiments and FE-simulations. Two experimental laboratory setups depending on the contact conditions in press hardening build the base for the wear models implemented in the FE-simulation to predict wear depths. The highest wear depth is found at the radius of the stamping tool and the discrepancies in wear predictions based on the two different laboratory test setups are analyzed.

  • 5.
    Deng, Liang
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Mozgovoy, Sergej
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Numerical study of contact conditions in press hardening for tool wear simulation2017Ingår i: International Journal of Material Forming, ISSN 1960-6206, E-ISSN 1960-6214, Vol. 10, nr 5, s. 717-727Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the press hardening industry, industrial and academic efforts are being directed toward predicting tool wear to realize an economical manufacturing process. Tool wear in press hardening is a tribological response to contact conditions such as pressure and sliding motion. However, these contact conditions are difficult to measure in-situ. Furthermore, press hardening involves high temperatures, and this increases the complexity of the tribo system. The present work investigated the contact conditions of press hardening with a commercial FE code (LS-DYNA) as a base for tool wear simulation. A press hardening experiment was established in industrial environments and evaluated through FE simulations. The numerical model was set up so as to approximate the manufacturing conditions as closely as possible, and the sensitivity with respect to the friction coefficients was examined. The influence of numerical factors such as the penalty value and mesh size on the contact conditions is discussed. The implementation of a modified Archard’s wear model in the FE simulation proved the possibility of tool wear simulation in press hardening. Finally, a comparison between the tool wear simulation and the measured wear depth is presented. 

  • 6.
    Deng, Liang
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Mozgovoy, Sergej
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Press-hardening thermo-mechanical conditions in the contact between blank and tool2013Ingår i: 4th International Conference Hot Sheet Metal Forming of High-performance Steel CHS: June 9-12, Luleå, Sweden : Proceedings / [ed] Mats Oldenburg; Braham Prakash; Kurt Steinhoff, Auerbach: Verlag Wissenschaftliche Scripten , 2013, s. 293-300Konferensbidrag (Refereegranskat)
  • 7.
    Deng, Liang
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Mozgovoy, Sergej
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Validation of tool-wear simulations based on a full-scale press hardening experiment2015Ingår i: Hot Sheet Metal Forming of High-Performance Steel 5th International Conference: May 31-June 3, Toronto, Canada : Proceedings / [ed] Kurt Steinhoff; Mats Oldenburg; Braham Prakash, Auerbach: Verlag Wissenschaftliche Scripten , 2015, s. 121-128Konferensbidrag (Refereegranskat)
    Abstract [en]

    To extend the service life of stamping tools for press hardening processes, tool wear prediction gradually becomes an important topic of concern in industry. However, wear simulations based on the finite element method are mainly developed in laboratory and the lack of validation of full-scale experiments restricts the proposal of an accurate wear model. The work presented in this paper aims at validating the used wear models for stamping tools through a full-scale press hardening experiment. The wear model in conjunction with finite element (FE) simulations are dependent on contact mechanics and the corresponding wear data is obtained from laboratory tests, where the test parameters are specified in ranges that accord with the contact conditions of press hardening. The full-scale press hardening experiment producing a dog-bone shaped part is run for 200 continuous strokes. Geometry updating of the stamping tool is used to investigate the influence of shape change on the pressure occurring on the tool. The results have shown that the geometry change of the stamping tool, after producing a large number of parts, causes changes in the contact pressures and therefore affects the wear simulation. In the end, the wear simulation results are compared to the preliminary result of the full-scale press hardening.

  • 8.
    Deng, Liang
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Mozgovoy, Sergej
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Simulation of tool shape change due to wear under press hardening conditions2015Ingår i: Proceedings of The Second International Conference on Advanced High Strength Steel and Press Hardening, Singapore: World Scientific and Engineering Academy and Society, 2015, s. 580-584Konferensbidrag (Övrigt vetenskapligt)
  • 9.
    Deng, Liang
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Mozgovoy, Sergej
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Wear Observations on Uncoated Tool and Workpiece Surfaces from a Full-Scale Press Hardening Wear Test2017Ingår i: Advanced High Strength Steel and Press Hardening / [ed] Zhang, Y; Ma, M, Singapore: World Scientific, 2017, s. 433-437Konferensbidrag (Refereegranskat)
    Abstract [en]

    Tool wear in press hardening has attracted researchers' attention and recently several papers have focused on the wear observations in the laboratory tests mimicking the press hardening conditions. However, the wear observations and quantification in full-scale press hardening tests are rare in view of high costs and longtime requirements. In this work, the wear behavior in a full-scale press hardening wear test has been studied in order to understand the wear mechanisms occurring in the stamping tool. Furthermore, the wear depths in the real stamping tool were measured by using a coordinate measurement machine (CMM) that can provide the quantified wear result and serve as a base to validate the possible wear model. The present study also includes the wear observations in both the counterparts i.e., the blank (workpiece) and the stamping tool with the aim of studying the transfer material/wear particles. Two common tool steels were used in the full-scale press hardening wear test and the differences in the wear severities were observed. Since abrasion and adhesion are major wear mechanisms previously in many laboratory tests, the present study identifies the wear evolution and mechanisms on uncoated tool and workpiece surfaces in the press hardening wear test.

  • 10.
    Deng, Liang
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Pelcastre, Leonardo
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    A Tribological Test under Press Hardening Conditions for Galling Research2017Ingår i: 6th International Conference Hot Sheet Metal Forming of High-Performance Steel CHS2: June 4-7 2017, Atlanta, Georgia, USA : proceedings / [ed] Mats Oldenburg, Braham Prakash, Kurt Steinhoff, Warrendale, PA: Association for Iron & Steel Technology, AIST , 2017, s. 453-460Konferensbidrag (Refereegranskat)
  • 11.
    Deng, Liang
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Pelcastre, Leonardo
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Experimental Evaluation of Galling Under Press Hardening Conditions2018Ingår i: Tribology letters, ISSN 1023-8883, E-ISSN 1573-2711, Vol. 66, nr 3, artikel-id 93Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Severe adhesion, also referred to as galling, is a critical problem in press hardening, especially in stamping tools used for hot forming of Al–Si-coated ultra-high strength steel. Galling is known to develop rapidly on the tool surface and it negatively affects the quality of the formed products. Earlier research on this topic has focused on the galling initiation. However, studies on the galling development during extended sliding and the corresponding quantitative measurement still lack depth. In the present study, a tribological test is established to study the galling development under press hardening conditions. The tribological test set-up aims to simulate extended sliding between the Al–Si-coated boron steels and the tool die material. The contact conditions in the interface are studied by a numerical model of the tribological test. The friction coefficients and material transfer are discussed taking into account the variation of the different test conditions. Using the results from the tribological tests, the galling simulation is performed in the numerical model. A geometry-updated sample based on the galling (transferred material build-up) height is simulated and the consequent pressure fluctuation is obtained in the numerical model. This contributes to the explanation of the severe transferred material accumulation during the test.

  • 12.
    Deng, Liang
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Pelcastre, Leonardo
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Numerical investigation of galling in a press hardening experiment with AlSi-coated workpieces2019Ingår i: Engineering Failure Analysis, ISSN 1350-6307, E-ISSN 1873-1961, Vol. 99, s. 85-96Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Press hardened steels are commonly used as a lightweight choice for manufacturing car components because of the high ratio of strength to weight. The use of ultra-high-strength steels for the design of lightweight vehicles contributes to the reduction of emissions of carbon dioxide while maintaining passenger safety. Stamping tools used in press hardening processes suffer harsh contact conditionsin terms of dramatic temperature changes, cyclic loadings, and complex interactions between coatings and oxidation. In mass production, tool wear is an inevitable problem that increases maintenance costs. Severe adhesive wear, also called galling, substantially occurs in the stamping tool used against Al—Si-coated workpieces. The galling that takes place during press hardening not only degrades the production quality but also shortens the service life of the tool. In order to properly arrange tool maintenance and minimize galling through adjusting process parameters, engineers need to know when and where galling occurs, based on modelling of the galling in press hardening simulations. In order to implement a galling simulation for press hardening, a modified Archard wear model is employed in the present study, which is a contact-mechanics-based model. The specific wear rate in the model is calibrated by the quantitative galling measurements of a high-temperature tribometer test. The tribological test is designed to mimic the press hardening conditions, where the correlations between galling and process parameters such as temperature, pressure, and sliding distance are outlined. The galling simulation is implemented in a full-scale press hardening experiment, and the predicted galling is validated in terms of severe galling positions and galling profiles. The galling profile evolution is correlated to variations in the contact conditions. Uncertainties in the numerical model, such as the choice of penalty scaling factor and friction coefficient, are analysed with a parameter study and discussed. This study demonstrates finite element (FE) simulations involving galling prediction in press hardening so as to improve product development and production efficiency.

  • 13.
    Mozgovoy, Sergej
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Deng, Liang
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Effect of temperature on friction and wear of prehardened tool steel during sliding against 22MnB5 steel2013Konferensbidrag (Refereegranskat)
  • 14.
    Mozgovoy, Sergej
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Deng, Liang
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Effect of temperature on friction and wear of prehardened tool steel during sliding against 22MnB5 steel2014Ingår i: Tribology - Materials, Surfaces & Interfaces, ISSN 1751-5831, E-ISSN 1751-584X, Vol. 8, nr 2, s. 65-73Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mechanical components in tribological systems exposed to elevated temperatures are gaining increased attention since more and more systems are designed to operate under extreme conditions. In hot metal forming, the effect of temperature on friction and wear is especially important since it is directly related to process economy (tool wear) and quality of the produced parts (friction between tool and workpiece). This study is therefore focused on fundamental understanding pertaining to the tribological characteristics of prehardened hot work tool steel during sliding against 22MnB5 boron steel. The tribological tests were carried out using a high temperature reciprocating sliding friction and wear tester under a normal load of 31 N (corresponding to a contact pressure of 10 MPa), a sliding speed of 0·2 m s−1 and temperatures ranging from 40°C to 800°C. It was found that friction coefficient and specific wear rate decreased at elevated temperature because of formation of compacted wear debris layers on the surfaces.

  • 15.
    Mozgovoy, Sergej
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Deng, Liang
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Simulative High Temperature Friction and Wear Studies for Press Hardening Applications2015Ingår i: Hot Sheet Metal Forming of High-Performance Steel 5th International Conference: May 31-June 3, Toronto, Canada : Proceedings / [ed] Kurt Steinhoff; Mats Oldenburg; Braham Prakash, Auerbach: Verlag Wissenschaftliche Scripten , 2015, s. 167-175Konferensbidrag (Refereegranskat)
    Abstract [en]

    Press hardening is employed in automotive industry to produce advanced high-strength steel components for safety and structural applications. In this hot forming process, the dimensional accuracy of produced components relies not only on an optimum friction level for the deformation of the workpiece, but it also gets affected by wear of the forming tools, which reduces the service life of the tool as well. It is desirable to enhance the durability of the tools by understanding the influence of contact conditions on tool wear. However, this is difficult to achieve in conventional tribological testing equipment. With this in view, the tribological behaviour of tool-workpiece material pairs at elevated temperatures has been studied in a newly developed experimental set-up simulating the conditions prevalent during interaction of the hot workpiece with the tool surface. The coefficients of friction of uncoated and Al-Si coated 22MnB5 steel decreased when the normal load increased. The influence of sliding velocity on the coefficient of friction was negligible for uncoated and Al-Si coated 22MnB5 steel. In the case of Al-Si coated 22MnB5 steel, adhesive material transfer of the Al-Si coating onto the tool steel surface was the main wear mechanism and this was also the reason for the higher and unstable friction coefficient when compared to uncoated 22MnB5 steel. In the case of uncoated 22MnB5 steel, adhesion was the main wear mechanism.

  • 16.
    Mozgovoy, Sergej
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Hardell, Jens
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Deng, Liang
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Oldenburg, Mats
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Material- och solidmekanik.
    Prakash, Braham
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Tribological Behavior of Tool Steel under Press Hardening Conditions Using Simulative Tests2018Ingår i: Journal of tribology, ISSN 0742-4787, E-ISSN 1528-8897, Vol. 140, nr 1, artikel-id 011606Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Press hardening is employed in the automotive industry to produce advanced high-strength steel components for safety and structural applications. This hot forming process depends on friction as it controls the deformation of the sheet. However, friction is also associated with wear of the forming tools. Tool wear is a critical issue when it comes to the dimensional accuracy of the produced components and it reduces the service life of the tool. It is therefore desirable to enhance the durability of the tools by studying the influence of high contact pressures, cyclic thermal loading, and repetitive mechanical loading on tool wear. This is difficult to achieve in conventional tribological testing devices. Therefore, the tribological behavior of tool-workpiece material pairs at elevated temperatures was studied in a newly developed experimental setup simulating the conditions prevalent during interaction of the hot sheet with the tool surface. Uncoated 22MnB5 steel and aluminum-silicon (Al-Si)-coated 22MnB5 steel were tested at 750 °C and 920 °C, respectively. It was found that higher loads led to lower and more stable friction coefficients independent of sliding velocity or surface material. The influence of sliding velocity on the coefficient of friction was only marginal. In the case of Al-Si-coated 22MnB5, the friction coefficient was generally higher and unstable due to transfer of Al-Si coating material to the tool. Adhesion was the main wear mechanism in the case of uncoated 22MnB5

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